The ex-Swansea City and Leeds United manager was only appointed as Aitor Karanka's successor on Teeside in the summer, but has failed to make Boro title contenders in the Championship so far this season.
Boro currently find themselves languishing in ninth position in the standings - 18 points off current leaders Wolves - with only eight wins attained from 20 matches, and Monk's position at the club is now under increasing scrutiny.
The club's chairman Steve Gibson had promised Boro's fanbase that Monk and his charges would "smash the Championship" after he bankrolled a summer spending spree including the big-money captures of Britt Assombalonga and Martin Braithwaite.
Three defeats in the past seven league games have left Boro seven points off the last play-off place and, while the points tally of seven between them and sixth-placed Derby isn't insurmountable, fans are growing restless over their team's inconsistent form.
Gibson is reportedly looking for a vast improvement in results from Monk throughout December despite now being labelled 100-1 outsiders to win the title, and the 38-year-old will be expected to take at least 11 points from his side's next five fixtures.
A home clash against Ipswich Town is followed by trips to Millwall and Sheffield Wednesday, before home encounters with Bolton and Aston Villa on 26th and 30th December see out the month for Middlesbrough.
Failure to win their home games and any defeat on the road would see Boro slip even further away from the promotion spots, and Monk could even find himself out of work at the turn of the year if he doesn't get their season back on track.